Conventional board work devices such as mounting devices that mount components on a circuit board are well-known. Also known are mounting devices provided with two lanes that convey boards. For example, in the mounting device disclosed in patent literature 1, when mounting components on two boards held in a first lane and a second lane, component mounting operation is performed first on the board that is loaded first. With this device, if a state arises in which component mounting operation on the latter board becomes possible before component mounting operation on the initial board has finished, a component that is a target for component mounting operation to the initial board becomes a mounting start component for the latter board at this point. By doing this, with this device, the frequency of work required when changing component types is decreased. Note that, with this device, it is determined whether component mounting operation is possible on the latter board by using the board detection signal of a board sensor that detects whether the board has been positioned correctly at the mounting position.